Despite the New South Wales premier having asked the authority to investigate allegations raised by Four Corners that misinformation had been taught to students, a board member of the New South Wales Education Standards Authority (NESA) has spoken out in support of a group of Opus Dei-aligned Sydney schools.

An ABC Four Corners program to be broadcast on Monday will investigate instances of students at Pared schools in the Sydney's Hills district being taught misinformation about sexual health, including that pornography causes holes in the brain, that girls were being discouraged from getting the HPV cervical cancer vaccine, and that students are subjected to persistent attempts to recruit them to Opus Dei, a small-but-powerful Catholic organisation.

NESA board member Dallas McInerney — who is also a member of the New South Wales Liberal party — was quoted in the Sydney Morning Herald about the forthcoming story, saying that the ABC has a "wider agenda".

He also said the schools were "good local schools" and are "doing good work on behalf of their students and families".

Mr McInerney is the chief executive of Catholic Schools NSW, which does not govern the schools — Tangara School for Girls and Redfield College.

The independent schools follow the principles of Opus Dei's Josemaria Escriva and were set up by a group of parents in the 1980s who formed the Pared Foundation which governs them.

NSW Teachers Federation president Angelo Gavrielatos said Mr McInerney's comments could be seen as prejudicial.

"Given that the statutory legal authority — NESA — has announced an investigation, it is improper that a member of the NESA board has made comments on the matter that could be construed as prejudicial to that investigation," Mr Gavrielatos said.

"Major concerns have been raised about the wellbeing of students at these schools.

"NESA has a statutory, legal responsibility to examine these matters thoroughly, as it has done at other schools in the past," he said.

This week, ABC's Four Corners put questions to New South Wales Premier Dominic Perrottet and, in response, a spokesperson described the allegations as serious.

"The premier has referred the allegations to the NSW Education Standards Authority (NESA)," the spokesperson said.

"The allegations should be investigated by the appropriate state body."

ABC's Four Corners asked NESA whether the public could have confidence in its ability to conduct an independent investigation, in light of Mr McInerney's comments.

In a statement, a spokesperson for NESA said: "All investigations are carried out by staff independent of the board."

NESA said that its board members hold a number of positions outside their membership and are able to make comments as spokespeople for other roles.

The spokesperson also said that NESA had not, prior to this week, received formal complaints about Pared schools that warranted an investigation in line with school registration requirements.

However, NESA's complaints policy dictates that people with complaints about independent schools must first raise those complaints with the school board.

"Complaints about a non-government school can be made to NESA at any time, provided there is clear evidence that options for pursuing the complaint at the school have been pursued without resolution or that there is a compelling reason that this would not be appropriate," its policy states.

ABC's Four Corners has interviewed a former student of a Pared school, who contacted NESA with a complaint, and was told she needed to first contact the schools, which she felt was futile. She says she and her mother contacted the authority on several occasions between 2018 and 2022.

In a statement, a spokesperson for Mr Perrottet said: "NESA is an independent body and undertake their work independently."

Watch ABC's Four Corners' 'Purity: An education in Opus Dei' Monday night on ABC TV and iview.